The IEEE 1394 standard, "P1394 Standard For A High Performance Serial Bus," Draft 8.0v2, Jul. 7, 1995, is an international standard for implementing an inexpensive high-speed serial bus architecture which supports both asynchronous and isochronous format data transfers. Isochronous data transfers are real-time transfers which take place such that the time intervals between significant instances have the same duration at both the transmitting and receiving applications. Each packet of data transferred isochronously is transferred in its own time period.
An example of an ideal application for the transfer of data isochronously would be from a video recorder to a television set. The video recorder records images and sounds and saves the data in discrete chunks or packets. The video recorder then transfers each packet, representing the image and sound recorded over a limited time period, during that time period, for display by the television set. The IEEE 1394 standard bus architecture provides multiple channels for isochronous data transfer between applications. A six bit channel number is broadcast with the data to ensure reception by the appropriate application. This allows multiple applications to simultaneously transmit isochronous data across the bus structure. Asynchronous transfers are traditional data transfer operations which take place as soon as possible and transfer an amount of data from a source to a destination.
The IEEE 1394 standard provides a high-speed serial bus for interconnecting digital devices thereby providing a universal I/O connection. The IEEE 1394 standard defines a digital interface for the applications thereby eliminating the need for an application to convert digital data to analog data before it is transmitted across the bus. Correspondingly, a receiving application will receive digital data from the bus, not analog data, and will therefore not be required to convert analog data to digital data. The cable required by the IEEE 1394 standard is very thin in size compared to other bulkier cables used to connect such devices. Devices can be added and removed from an IEEE 1394 bus while the bus is active. If a device is so added or removed the bus will then automatically reconfigure itself for transmitting data between the then existing nodes. A node is considered a logical entity with a unique address on the bus structure. Each node provides an identification ROM, a standardized set of control registers and its own address space.
The IEEE 1394 cable environment is a network of nodes connected by point-to-point links, including a port on each node's physical connection and the cable between them. The physical topology for the cable environment of an IEEE 1394 serial bus is a non-cyclic network of multiple ports, with finite branches. The primary restriction on the cable environment is that nodes must be connected together without forming any closed loops.
The IEEE 1394 cables connect ports together on different nodes. Each port includes terminators, transceivers and simple logic. A node can have multiple ports at its physical connection. The cable and ports act as bus repeaters between the nodes to simulate a single logical bus. The cable physical connection at each node includes one or more ports, arbitration logic, a resynchronizer and an encoder. Each of the ports provide the cable media interface into which the cable connector is connected. The arbitration logic provides access to the bus for the node. The resynchronizer takes received data-strobe encoded data bits and generates data bits synchronized to a local clock for use by the applications within the node. The encoder takes either data being transmitted by the node or data received by the resynchronizer, which is addressed to another node, and encodes it in data-strobe format for transmission across the IEEE 1394 serial bus. Using these components, the cable physical connection translates the physical point-to-point topology of the cable environment into a virtual broadcast bus, which is expected by higher layers of the system. This is accomplished by taking all data received on one port of the physical connection, resynchronizing the data to a local clock and repeating the data out of all of the other ports from the physical connection.
Existing televisions and personal computer (PC) monitors are very different. Televisions generally have a medium display resolution capability and several analog interfaces for receiving input signals, such as a composite video interface, an s-video interface and a radio frequency interface for radio frequency signals received over coaxial cable. Although, televisions are advancing in their ability to display increasingly higher resolutions of video and graphic data, consumer video resolution has changed little over time. While the picture tube of PC monitors is based on consumer television technology, PC monitors or displays have very different resolution requirements than consumer televisions, due to the need for PC monitors to have the ability to display legible small text and fine lines for detailed work. To meet this need, PC monitors have a higher resolution than consumer televisions and very different high bandwidth interfaces, such as Video Graphics Array (VGA), Super VGA (SVGA) and RGB.
Existing televisions with a picture-in-picture feature allow two video inputs to be viewed simultaneously on the television screen. For example, a viewer using the picture-in-picture feature is able to simultaneously view video signals from two different sources, e.g., from cable and from a video cassette recorder (VCR). However, control of the operation of each source of display is achieved through that source. Therefore, when controlling an external source such as a VCR, control signals from a remote control device must be directed towards that source.
What is needed is a display device that allows a user to display multiple display windows each driven by a device and control operation of the driving devices through the display. What is also needed is a single control interface to achieve these benefits.